Brian--
Thanks for the photos! Obviously this works, and gives greater credibility to the concept of the potential for the knife to be used for defensive, as well as utilitarian, purposes. Of the dozen or so knives that I've handled that have indisputable Scottish provenance, only three had sheaths, and none of those had belt hooks. Since belt hooks were a common feature on Scottish pistols, it would (I think) be reasonable to assume that they would feature on the sheathes of small, personal knives, such as the one owned by your wife (and pictured on this thread). Certainly it would be just about the only practical way of securing the knife to one's person, no matter how, or where, worn.

I am still somewhat dubious about the primary role of the knife as a concealed weapon; in an age and at a time when flatware (or cutlery, as some term it) was not ubiquitous in most households, it was not at all uncommon for a guest to bring his own spoon and knife-- and this continued into the 18th century. Given the manner of dress of the Highland Scots at this time, I would tend to think that tucked away under the arm and close to the body would be the most convenient place to carry a knife primarily intended for domestic duties.

Outside of the Highlands, where the carrying of a dirk well suited to self defense was not normally done, it could very well be that gentlemen did carry such a knife as much for protection as anything else.

As Jim Bowie was of Scots descent, it is a pity that none of his ancestors wrote a book on Scottish dirks, daggers, and knives. Then we'd know for sure.